betting for value

[Wacken]

please tell my if my idea is correct.

You flop a nut flush draw with 4 players still in. With 4 players, it is correct to do a bet for value. However suppose the flop are all low cards, there is no reasonable str8 posibility and 2 people will fold after your bet. Making them fold will probably not drastically improve your winning chances here. If you don't get the flush, you might have the best hand, but chances are not great, out of 4 players, the one caller is pretty likely to have a better hand than that, espescially if you have a low kicker.
Now instead of getting more money in the pot, you scared out potential bets for the turn and river.

I would guess in this situation this value bet is -EV. Am i correct that you should only make a value bet if you expect most or everyone to call? (or expect everyone to fold instead of all but one)

[joda mas]

This is true if your flush draw is small. If you hold overcards, gettting people to fold may allow you to win with a big pair.

By the way, if 2 people call, it's not that bad since you will hit your flush better than 2:1. If only 1 calls than it's -ev without overcards.

Betting may drive out a bigger ace (thereby earning you 3 more outs), or may earn you a free card on the turn. If people are just calling your bets (and you are not overly aggressive in general), then they may be drawing to the same hand you are, and will fold even if they manage to hit a low pair on the end. Betting is usually a better option because it means you have another way of winning if you miss, and that's when everyone folds.